Why is my HP Envoy printer printing faintly when connected to iMac?

My HP Envoy printer will print a complete test page with all colors, filling the entire page, which means the print heads are not clogged. However, when I go to print a document, it will either print faintly in color, if asked, or in black and fades. It will not print a document at all if asked to print a page. It comes out blank. So my iMac and the printer are connected but not talking to each other correctly? Has anyone else ran into this problem?

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